1. Field of the Invention
This invention relates to the self-condensation of aldehydes, the condensation of aldehydes with alcohol, the trimerization of aldehydes to produce alpha,beta-unsaturated aldehydes, acetals, and trioxanes respectively and the conversion of trioxanes to aldehydes in the presence of catalytic amounts of Group VIII metal salts.
Aldehydes, trioxanes, and acetals are widely used in the formation of resins, preservatives, dyes, and chemical intermediates.
Various acids and bases have been used as catalysts for such condensation reactions. Since alcohol dehydration is catalyzed by acids but not by bases, in a number of such cases the final result of the condensation may be determined by the nature of the catalyst used. Thus some base-catalyzed condensations are much more likely to stop at the stage of the aldol than is an acid catalyzed condensation.
The present invention describes a new process for the preparation of acetals, trioxanes, and alpha,beta-unsaturated aldehydes. This process is characterized by low temperature, liquid phase, homogeneously catalyzed reactions of aldehydes in the presence of Group VIII metal salt catalysts.
2. Description of the Prior Art
The acid- and base-catalyzed aldol condensations of aldehydes, as well as the acid-catalyzed condensation of aldehydes with alcohols, are well-known reactions and discussions concerning these reactions may be found in introductory organic chemistry text books. The following references are of special interest in that they teach high temperature, (i.e. 600.degree.-800.degree. F.) vapor phase, or heterogeneously catalyzed reactions wherever Group VIII metals are employed as catalysts for these reactions.
______________________________________ Aldol Condensations of Aldehydes Reference Catalyst Conditions.sup.a ______________________________________ 1) U.S. 2,549,508 Fe.sub.2 O.sub.3 V, 700.degree. F. 2) Ciola, R., Anais Cd(PO.sub.4).sub.2 V, 275.degree. C. Assoc. Brasil., Ni.sub.3 (PO.sub.4).sub.2 20, 63-76 (1961). 3) Nodzu, R., et al., Fe(OH).sub.3 V, 170.degree.-260.degree. C. J. Chem. Soc. Ni(OH).sub.2 Japan, 57, 914-16 (1954). 4) Dolgov, B. N., et Al.sub.2 O.sub.3 --Fe.sub.2 O.sub.3 V, 400.degree. C. al., Zhur., Obshchei Khim., 22, 950-3 (1952). Condensation of Aldehydes with Alcohols 1) Brit. 607,130 NH.sub.4 Cl C, 25.degree. C. 2) U.S. 2,451,949 Bauxite V, 0- 50.degree. C. fuller's earth 3) Fr. 868,182 H.sup.+ + CaCl.sub.2 C -- 4) Brit. 625,131 H.sub.2 SO.sub.4 C, 15- 20.degree. C. 5) U.S. 2,519,540 H.sub.2 SO.sub.4 C, 20.degree. C. 6) U.S. 2,691,684 none V, 350.degree. C. 7) Brit. 716,541 HCl C, 65.degree. C. 8) U.S. 2,782,177 Ni -- 9) U.S. 2,566,559 Cation ex- C, 30.degree. C. change resin ______________________________________ .sup.a C = condensed phase, V = vapor phase